"I think it's very valuable. It completely changes the way we think," Swass said.

Bristol Police as well as state police are doing about a dozen different real-world exercises, so if an incident like Newtown were to happen locally, they'd be equipped and prepared to handle the situation.

About two dozen high school students from Newfound Regional High School volunteered to participate in the exercise.

"It shows me that I know our school will be in safe hands if this does end up happening, ever happens, we'll be in safe hands," said senior Sara Vassy, who took part in the training.

The bullets in the officers guns were blanks and none of the weapons were fired while students were present.

Students said the experience was insightful, but it was a lesson they hope never unfolds in their classroom.

"It was pretty realistic and sort of a scary thought if that were to really happen," said Tyler Maviki, a junior at the school.

Over the past 10 years, hundreds of officers across the state have gone through similar training.

Bristol Police planned this exercise months ago, but after the school shooting in Newtown, Police Chief Mike Lewis made it a top priority.

He said he wants to make sure every member of his department has the training to protect students against any type of threat.